CPR associated with sudden cardiac death typically has a low rate of success. CPR is complicated by rescuer knowledge, technique, and endurance, which some automated devices have been shown to improve. However, effective perfusion of the most critical and metabolically demanding organs remains a limiting factor even during ideal resuscitation efforts.
Further, current resuscitation protocols involve the use of epinephrine and other vasoconstrictors to enhance blood flow to central organs. Nonetheless, epinephrine has been shown to cause myocardial necrosis and to be harmful when given in suboptimal doses during resuscitation. Epinephrine also has the unintended effect of making the aorta relatively more stiff, which diminishes blood flow distribution in a healthy person.